For group questing, you probably won't have trouble at all. But it's a very... wide-spread build, combining a melee DPS soul, a tank soul and a healing soul. Wouldn't seem like a very personally efficient build. However, bear in mind that you won't be stuck with the three souls you initially choose. By level 13 you can start unlocking the rest of your calling's souls and you won't be going to any dungeons until about level 16-18 or so. By then, you should have unlocked a few souls and probably purchased your second role (it's only 30g), so you can put together a dedicated healing build.
So if you wanted a strong melee DPS build with a little bit of off-healing to help keep your Paladin buddy alive while questing together, I'd recommend Shaman/Druid/Warden (mostly because I'm a fan of HoTs while questing, but also the Warden's water theme sort of matches the Shaman's Ice and Lightning theme. The Druid's just there for passive benefits.)
At 0 points, the Warden gives you access to an instant HoT and a long-ranged instant water damage spell, which is great for picking up mobs from range. At two points in to Warden, you also get a cast-time heal that heals for a decent chunk immediately followed by some more healing over time. Plus the fairy's HoT.
Here is a sample build for level 15: http://rift.zam.com/en/stc.html?t=00ane.c.VLzx.M
It's also worth noting that the Shaman deals substantially more damage at earlier levels compared to the Druid. I believe it balances out later on, but Druid's don't get most of their stronger stuff until later whereas Shamans start getting fairly powerful attacks very early on.
EDIT: It's also worth mentioning that I have a deep-Warden build for dungeons, and with a level 18 Riftstalker tank, I had to spam my heals quite constantly, so a hybrid DPS/Heals build probably won't be good at all for dungeons. Edited, Feb 28th 2011 10:14am by Neuroticaine
All Characters on Aedraxis - Defiant-side.
Neuroticaine - Level 19 Cleric (Shaman)
Rhayge - Level 10 Warrior (Reaver)
Veyne - Level 10 Mage (Archon)
Sevrys - Level 15 Rogue (Assassin)